Longitudinal Negative Magnetoresistance and Magnetotransport Phenomena in Conventional and Topological Conductors

Recently, a large negative longitudinal (parallel to the magnetic field) magnetoresistance was observed in Weyl and Dirac semimetals. It is believed to be related to the chiral anomaly associated with topological electron band structure of these materials. We show that in a certain range of parameters such a phenomenon can also exist in conventional centrosymmetric and time-reversal invariant conductors, lacking topological protection of the electron spectrum and the chiral anomaly. We also discuss the magnetic field enhancement of the longitudinal components of the thermal conductivity and thermoelectric tensors.

Figure 1

Landau level spectrum of the Dirac equation in the gapless case $E_g=0$ [panel (a)] and the gapped case [panel (b)]. All Landau levels except the lowest one are degenerate in helicity and are shown by solid blue lines. The lowest Landau level is nondegenerate. The helicity of electronic states in it is indicated by the line style: Positive helicity states are shown by the green dashed line, and negative helicity states by the black dash-dotted line. The red horizontal line indicates the location of the chemical potential.